cgi - Python deadlock error - Trying to retrieve key value from shelve -

here code updating record in shelve

def updaterecord(db, form):     if not 'key' in form:         fields = dict.fromkeys(fieldnames, '?')         fields['key'] = 'missing key input'     else:         key = form['key'].value         if key in db:             record = db[key]         else:             person import person             record = person(name='?',age='?')         field in fieldnames:             setattr(record, field, eval(form[field].value))         db[key] = record         fields = record.__dict__         fields['key'] = key     return fields 

when trying retrieve value shelve getting error

>>> import shelve >>> db = shelve.open('class-shelve') >>> db['sue'].name traceback (most recent call last):   file "<stdin>", line 1, in <module>   file "/usr/lib/python2.7/shelve.py", line 121, in __getitem__     f = stringio(self.dict[key])   file "/usr/lib/python2.7/bsddb/__init__.py", line 270, in __getitem__     return _deadlockwrap(lambda: self.db[key])  # self.db[key]   file "/usr/lib/python2.7/bsddb/dbutils.py", line 68, in deadlockwrap     return function(*_args, **_kwargs)   file "/usr/lib/python2.7/bsddb/__init__.py", line 270, in <lambda>     return _deadlockwrap(lambda: self.db[key])  # self.db[key] keyerror: 'sue' 

any insights whats going on?

assuming in first snippet, db variable 'shelf' object, then, although line...

db[key] = record 

...will add new key/value pair 'shelf', won't flush contents disk, won't available other processes sharing same 'shelf file'.

you can force 'shelf file' written disk adding line...

db.sync() 

...after adding new key/value pair, can quite slow when 'shelf file' gets large, may not want call frequently.